Benzopyran derivatives as the aglycon moiety of the 7-glycosyloxybenzopyran derivatives of the present invention have been disclosed for example in EP-A-0598117 by the present inventors, and similar benzopyran derivatives for example in J. Med. Chem., vol.31, pp.1473-1445, 1988, by Donald T. Witiak and in U.S. Pat. No. 4,845,121, but nothing about the 3- or 4-glycosyloxybenzopyran derivatives as their 7-position glycosides. In addition to this, nothing is known about the antiallergic activity of the 7-glycosyloxybenzopyran derivatives of the present invention and physiologically acceptable salts thereof.
Since antiallergic agents so far available commercially are not satisfactory in terms of efficiency, safety and bioavailability, studies on the development of antiallergic agents have been carried out: extensively. For example, a typical antiallergic agent, Tranilast (general name), requires high-dose administration for care of allergic disease, though its acute toxicity value (LD.sub.50) in mice is low (780 mg/kg), hence causing a problem of requiring caution at the time of its use because of the closeness between quantities of its efficacy and toxicity, namely its narrow safety range. Also, Disodium Cromoglicate (general name) as a well known antiasthamtic agent whose efficacy has been confirmed clinically is satisfactory in terms of its toxicity, but must be used by spray inhalation due to its extremely poor gastrointestinal absorbability. In addition, these known antiallergic agents are not effective on delayed type allergy, though they are effective on immediate type allergy. Chronic state of allergic diseases including asthma and atopic dermatitis is a serious problem, and the delayed type allergy is deeply concerned in the development of the chronic state. In consequence, a drug which is effective on both immediate type allergy and delayed type allergy is desirable as an antiallergic agent. As it is universally known, steroid is effective on both immediate type allergy and delayed type allergy but cause extremely serious side effects.
As has been described above, most of the antiallergic agents so far reported have various disadvantages, because they cannot show sufficient therapeutic effect because of the lack of efficacy on delayed type allergy, they are low in safety due to their narrow safety range, or their administration method is limited because of their poor gastrointestinal absorbability. In consequence, great concern has been directed toward the development of a drug which can be used in oral administration, has low toxicity and is effective on both immediate and delayed type allergies.
The inventors of the present invention have provided, by EP-A-0598117, a benzopyran derivative and an antiallergy agent which comprises the derivative as an active ingredient. This time, taking the aforementioned problems involved in the prior art into consideration, we contemplate providing a novel substance more useful as a drug and an antiallergic agent having low toxicity and excellent effect.